Remove evergreen client from buildscripts

All uses of the local evergreen client in buildscripts have been removed from the mongo repository (except a metrics script that is not currently being used) in favor of evergreen.py. We should remove the metrics script and client so that we no longer have to maintain them and no one accidentally starts using them.

As a server engineer,
I want the local evergreen client code removed,
so that I no longer have to maintain it.

AC:

• `buildscripts/client/evergreen.py` is removed.
• all tests and dependencies on `buildscripts/client/evergreen.py` are removed.